Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a golf ball. More specifically, the present invention relates to a golf ball with an oxygen barrier layer to prevent oxidation of an oxygen sensitive core.
2. Description of the Related Art
The core of the golf ball is the xe2x80x9cenginexe2x80x9d for the golf ball such that the inherent properties of the core will strongly determine the initial velocity and distance of the golf ball, and to a lesser extent the spin and feel of the golf ball. A higher initial velocity will usually result in a greater overall distance for a golf ball. In this regard, the Rules of Golf, approved by the United States Golf Association (xe2x80x9cUSGAxe2x80x9d) and The Royal and Ancient Golf Club of Saint Andrews, limits the initial velocity of a golf ball to 250 feet (76.2 m) per second (a two percent maximum tolerance allows for an initial velocity of 255 per second) and the overall distance to 280 yards (256 m) plus a six percent tolerance for a total distance of 296.8 yards (the six percent tolerance may be lowered to four percent). A complete description of the Rules of Golf are available on the USGA web page at www.usga.org. Thus, the initial velocity and overall distance of a golf ball must not exceed these limits in order to conform to the Rules of Golf. Therefore, the core for a USGA approved golf ball is constructed to enable the golf ball to meet, yet not exceed, these limits.
The coefficient of restitution (xe2x80x9cCORxe2x80x9d) is a measure of the resilience of a golf ball. The COR is a measure of the ratio of the relative velocity of the golf ball after direct impact with a hard surface to the relative velocity before impact with the hard surface. The COR may vary from 0 to 1, with 1 equivalent to a completely elastic collision and 0 equivalent to a completely inelastic collision. A golf ball having a COR value closer to 1 will generally correspond to a golf ball having a higher initial velocity and a greater overall distance. If the golf ball has a high COR (more elastic), then the initial velocity of the golf ball will be greater than if the golf ball had a low COR. In general, a lower Rhiele compression core will result in a higher COR value if the core is not degraded by oxidation.
The golf ball cores may be hollow, liquid filled or solid. Most solid cores are generally composed of a blend of a base rubber, a cross-linking agent, a free radical initiator, and one or more fillers or processing aids. A preferred base rubber is a polybutadiene having a high cis-1,4 content since the polybutadiene provides the desire COR for greater initial velocity.
However, polybutadiene and other base rubbers are highly susceptible to oxidation which changes the morphology of the polybutadiene that results in lower COR, increased Rhiele compression (the balls becomes softer), and possibly physical degradation of the material.
Ionomers and polyprolyene materials act as oxygen barriers, however, the thickness of these materials have adverse affects on the performance of a golf ball. For example, many golf balls have a polybutadiene core and a cover composed of a SURLYN(copyright) ionomer material. The thickness of the cover is usually 2 millimeters to 5 millimeters, and thus, greatly affects the performance of a golf ball. Ionomer materials are typically hard, on a Shore D scale, and have durability problems. Nevertheless, ionomer materials of this particular thickness do in fact provide an oxygen barrier for a polybutadiene core.
However, golfers demand golf balls with more than an ionomer cover on a polybutadiene core. Golfers want a durable cover, with a soft feel over a high energy core.
The present invention is able to overcome the problems of the prior art by providing a golf ball with an oxygen susceptible core, an oxygen permeable cover, and an oxygen barrier layer juxtaposed by the core and the cover. The oxygen barrier layer is preferably a thin film of ethylene vinyl alcohol copolymer which does not affect the performance of the golf ball, and is mechanically strong to withstand the manufacturing process for the golf ball.
One aspect of the present invention is a golf ball having a core, an oxygen barrier layer and a cover. The core is composed of polymer that is susceptible to oxidation. The oxygen barrier layer encompasses the core and has a thickness of less than 1 millimeter. The cover encompasses the oxygen barrier layer and is composed of an oxygen permeable material.
Another aspect of the present invention is golf ball having a polybutadiene core, an oxygen barrier film, and a polyurethane cover. The polybutadiene core has a diameter that ranges from 30 millimeters to 40 millimeters. The oxygen barrier film encompasses the core has a thickness of less than 1 millimeter and is composed of an ethylene vinyl alcohol copolymer. The cover encompasses the oxygen barrier film and has a thickness in the range of 0.5 millimeters to 3.5 millimeters. The cover may be thermosetting polyurethane, thermoplastic polyurethane, or other similar materials such as HYLENE(copyright), PEBAX(copyright) and HYTREL(copyright). The cover may be manufactured by injection molding, compression molding or casting.
Another aspect of the present invention is a method for producing a golf ball with an oxygen permeable cover. The method includes encompassing a core slug of an oxygen susceptible material within at least one sheet of an oxygen barrier film. The method also includes placing the core slug and oxygen barrier film within a mold and molding the core slug into a spherical core encompassed within the oxygen barrier film. The method also includes covering the spherical core and oxygen barrier film with a cover composed of an oxygen permeable material.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.